Catalytic dehydrogenation process



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United States Patent ()fitice 3,667,272 Patented Dec. 4, 1962 No Drawing. Filed Dec. 30, 1969, Ser. No. 79,527 11 Claims. (Ci. 260-4580) This invention relates to a new catalytic dehydrogenation process which is particularly useful for the production of butadiene and/ or isoprene.

The most used commercial process for the production of butadiene and isoprene involves the catalytic dehydrogenation of butylene and .amylenes with an iron oxide :catalyst promoted with sizeable amounts of potassium .carbonate and generally a small amount of chromium oxide. This process requires that the dehydrogenation be effected in the presence of a large excess of steam. Although the patent literature indicates steam to oefin mole ratios as low as 1 to 1, it is well known that much higher ratios are required for efiicient operation. In commercial practice this ratio is above at least 8 to 1 and generally around 12 to 1.

In the hitherto used commercial process quite high reaction temperatures are required. The range used commercially generally falls between about 590 and 650 C. At these high temperatures and in the presence of the large amounts of steam the activity of the catalyst is maintained by the continuous removal of carbonaceous deposits from the catalyst by the steam-carbon reaction which is catalyzed by the potassium carbonate in the catalyst. Thus the potassium carbonate is an essential ingredient.

An important factor in the production of butadiene and/or isoprene by dehydrogenation is the selectivity of the dehydrogenation process. The percent selectivity is defined as 100 times the moles of desired product produced divided by the moles of feed stock destroyed or otherwise converted. In order to obtain a reasonable selectivity the prior commercial process requires the use of low pressures. Generally pressures between about and 25 p.s.i.a. are used. This necessitates large equipment and complicates the recovery of the product. At these low pressures and under otherwise near optimum conditions, a selectivity around 80% may be obtained at a total conversion around 20% in the dehydrogenation of butylene to butadiene. The operations are sometimes conducted under conditions of temperature and space velocity to obtain conversions as high as about 35%, but generally somewhat lower conversions are preferred because the selectivity drops sharply as the conversion is increased. At 40% conversion the selectivity may be of the hitherto used process is that the conversion must be limited to quite low values (.about 25%) and this requires the working up of large amounts of material to recover the product and requires a sizeable recycle which further increases the size of the equipment.

One of the reasons for the inability of the presently used commercial process to operate at higher conversion is that the reaction, which (for the production of butadiene from butene-l) may be illustrated as follows:

catalyst is inhibited by the hydrogen liberated. If the hydrogen -were removed much higher conversions could be used.

One further shortcoming of the present commercial process is that due to the content of potassium carbonate in the catalyst, the catalyst is very hygroscopic and becomes soft if exposed to the atmosphere. This introduces difficulties in loading the reactors and also other inconveniences.

Thus, one of the major shortcomings genation of normal butane.

The object of the present invention is to provide a new and improved process for the catalytic dehydrogenation of aliphatic olefins, both acyclic and alicyclic, which contain at least four non-quaternary contiguous carbon atoms, such as normal butylene, tertiary amylenes, cyclopentene, and similar higher olefins having up to 6 or 7 carbon atoms, to corresponding polyolefins, including diolefins, which process has one or more of the following advantages:

(1) The process may be operated with comparatively little or no steam while still retaining the activity of the catalyst at a high level.

(.2) The process may be operated at considerably lower temperatures. Whereas it is important to quickly quench the reaction product from the quite high reaction temperature to a safe temperature in the hitherto used commercial process, this is not essential in the process of the present invention where lower temperatures can be used.

(3) Potassium carbonate is not an essential ingredient in the catalyst and in fact its presence is not recommended. Consequently the difficulties due to hygroscopicity of the catalyst are avoided.

(4) The process may be effected at comparatively higher pressures, thereby allowing smaller equipment to be used and facilitating the recovery of the product.

(5) The process may be operated at higher conversions without sacrifice of the selectivity. This last is considered the most important of the advantages mentioned.

In general outline these objects are obtained by the process of this invention, in which process a vaporized feed stream containing the olefin reactant to be dehydrogenated is contacted together with certain specified amounts of oxygen and preferably a small amount of steam at comparatively low temperatures between about 300 C. and 600 C. with a catalytic material containing indium compound in catalytically active amounts and the resultant vaporous product is treated in appropriate ways to recover the desired dehydrogenation product.

FEED STOCK The process of the present invention is principally of value .at present for the dehydrogenation of normal butylcues to butadiene and/or tertiary amylenes to isoprene but it can also be used to dehydrogenate cyclopentene to cyclopentadiene, normal amylenes to piperylene and higher olefins, e.g., hexenes and heptcnes, to the corresponding more unsaturated products. The normal butylene may be butene-l or butene-2, either cis or trans, or a mixture of normal butylenes such, for example, as can be separated from the products obtained in the cracking of petroleum oils or by the catalytic dehydro- The tertiary amylene may be any one or a mixture of the amylenes having one tertiary carbon atom. The feed stock may contain inert diluents such as any parafiinic or naphthenic hydrocarbon having up to about 10 carbon atoms.

One of the principal features of advantage of the present invention is that considerable amounts of propylene and isobutylene may be present in the feedstock, thereby eliminating the requirement for separating the feed stream to remove these hydrocarbons therefrom. It will be appreciated that although the catalytic material of the present invention does not produce any substantial amount of oxygenated organic materials under the conditions specified herein, it is nevertheless advantageous to maintain materials which may act only as inert diluents at a reasonable minimum for economic reasons.

STEAM The feed stock is preferably catalytically dehydrogenated in the presence of added steam, but it is to be emaoemva phasized that the presence of added steam is only a small benefit and is not essential. Recommended proportions of steam are from about 0.1 to 2 moles per mole of reactant, but as indicated, larger amounts can be used if desired and, on the other hand, steam can be altogether omitted.

OXYGEN In the process of the present invention a certain amount ofoxygen is passed with the feed stock through the reaction zone. Recommended amounts are from about 0.3 to 2.0 moles per mole of olefin reactant. The stoichiometric quantity is 0.5 mole per mole of olefin. It is preferred to use a stoichiometric excess, e.g., around 1 mole per mole of olefin. The oxygen may be supplied as pure or substantially pure oxygen, or air.

It is generally preferred to maintain the concentration of oxygen in the reactant mixture entering the reactor below about 12 v. percent although somewhat higher concentrations may be used if the concentration of the olefin reactant is at least about v. percent when operating at 30 p.s.i.g., at least v. percent when operating at 100 p.s.i.g. and at least about v. percent when operating at 300 p.s.i.g. Thus when using pure oxygen it is frequently desirable to dilute the mixture with an inert or substantially inert diluent which may be steam, vapors or paraflin hydrocarbons, CO or the like. On the other hand, if the amount of oxygen is such that it would constitute more than about 12 v. percent of the reaction mixture the oxygen may be introduced in increments, e.g., by injecting part of the oxygen separately into the reaction zone.

TEMPERATURE With the preferred catalyst the dehydrogenation becomes substantial at a minimum temperature around 300 C. The preferred temperatures are between about 350 C. and 500 C. Higher temperatures up to about 600 C. can be used, but only if efiicient means are provided to remove the exothermic heat of reaction. The temperatures mentioned are those near the reactor inlet. If a fixed bed of catalyst is used the temperature down stream will be several degrees, e.g., 80 C., higher.

PRESSURE The preferred pressure is near atmospheric, e.g. 5 to 75 p.s.i.a. On the other hand, higher pressures up to about 150 p.s.i.a. can be used and have the advantage of simplifying the product recovery.

SPACE VELOCITY In general the process of the present invention allows a higher space velocity to be used. Thus, comparatively small reactors and catalyst inventories can be used. For example, gaseous hourly space velocities up to about 20,000 may be employed While still obtaining reasonable conversions. Gaseous hourly space velocity, abbreviated GHSV, is defined as the volume of total feed vapor calculated under standard condition (STP) passed per hour per unit volume of the catalyst bed. A wide range of space velocities may be used. Generally space velocities between about 500 and 5000 are very satisfactory. Temperature, pressure, and space velocity should be jointly adjusted to obtain a conversion in the most favorable range, normally 4090%.

METHOD OF CONTACT The contact of the feed vapors, oxygen and steam, if any, is preferably effected by providing the catalyst in the form of a fixed foraminous bed of particles maintained at the reaction temperature and passing the feed vapors through the bed in a continuous or substantially continuous manner. In this method of operation the partial pressure of oxygen is high (maximum) at the inlet of the catalyst bed and declines toward the outlet. The con- Centration of diolefin product, on the other hand, is substantially zero at the inlet of the bed and maximum at the outlet. Thus, the concentration of oxygen is highest where the concentration of the desired product is lowest and the concentration of oxygen is lowest Where the concentration of the desired product is highest.

It is also possible to use the catalyst in powder form, but certain precautions should be taken. Thus, the powdered catalyst (e.g., passing a mesh U. S. standard sieve) can be dispersed in the reactant vapor mixture and the dispersion passed through the reaction zone. Alternatively, the reactant vapor mixture may be passed up through a fluidized bed of the catalyst. In such case the oxygen may be separately introduced into the bed.

The gaseous mixture issuing from the reaction zone may be quenched but this is normally not essential. Except in some cases when operating at the upper limit of the recommended temperatures there is little tendency for side reactions to take place. The eflluent is preferably cooled by indirect heat exchange with the feed and then washed with dilute caustic to neutralize the traces of organic acid present and condense and remove the steam. If air is used to supply the oxygen the remaining mixture is preferably compressed and scrubbed with oil to separate the hydrocarbons from the nitrogen, carbon dioxide, and carbon monoxide. The hydrocarbon may be stripped from the oil and subjected to an extractive distillation or a copper ammonium acetate treatment in the known manner to separate and recover the diolefin.

CATALYST The catalyst used in the process of the present invention differs materially from those used in the commercial process mentioned above. While the catalyst used in the present process may contain some iron oxide this oxide is by no means essential and when present it is used in much smaller concentrations than in the hitherto used catalysts. Also the catalyst used in the process of the present invention preferably contains no potassium carbonate, or the equivalent thereof, and the process does not depend at all upon the steam-carbon reaction to maintain catalyst activity. Nevertheless continuous operation is not only possible but also recommended.

The process of the present invention utilizes essentially a material represented herein as a composition of matter consisting of indium, oxygen and an element selected from the group consisting of phosphorus, molybdenum and tungsten in combined form. A preferred composition of matter having catalytic effect in the oxidative dehydrogenation reaction described herein will be referred to hereinafter as indium phosphate (InPO A description of indium phosphate is found in the Journal of the Chemical Society, 1960, pages 2452 through 2457, by Brownlow, Salmon and Wall. Whereas the designation indium phosphate (InPO is used to indicate one of the preferred catalytically active materials in the present invention, the composition may vary considerably from that represented by this exact formula. The catalyst may be considered as the compound 1nPO but may, on the other hand, include substantial amounts of indium oxide (In O in addition thereto. At any rate, the catalytic activity of the material of the invention must of necessity include a substantial amount of indium, oxygen and phosphorus, molybdenum or tungsten conveniently considered as an oxygen-containing radical and, as in the case of indium phosphate, for example, the phosphate (P0 radicals are visualized as being integral for the most part as InPO molecules. Moreover, other phosphates such as, for example, calcium phosphate, barium phosphate, or the like, may be present Without deleterious effect; such materials probably function principally as inert supporting media.

Various means for the preparation of the catalytic materials of the present invention will suggest themselves to those skilled in the art of catalyst preparation. The following are offered for the purpose of exposition only and various modifications thereof are contemplated with-t transformed to butadiene.

out departure from the spirit or scope of the invention. One method for the preparation of indium phosphate,

reacting phosphoric acid with solid indium nitrate. A

fourth suggested method involves the reaction of indium nitrate in solution with a soluble phosphate followed by an appropriate manipulation of pH as required. The Brownlow et .al. reference (supra) suggests a still further means for preparation of the catalytic material.

Indium-molybdate and indium tungstate catalysts may be prepared from reaction of indium salts with ammonium molybdate or ammonium tungstate or the corresponding oxides. The reactions may be carried out in solution at appropriate pH or in the solid state. Indium oxide may also be employed for solid state reactions. Various other ways of preparing these catalysts will suggest themselves to those skilled in the art. It is preferred to use indium nitrate and ammonium molybdate or tungstate, as in the subsequent examples, to .avoid the presence of non-volatile elements other than indium, molybdenum or tungsten. Ammonium hydroxide is a preferred alkali for precipitation, but other alkalis may sometimes be used to advantage.

Indium oxide may be prepared by oxidation of the metal, by precipitation from solutions of salts, by decomposition of nitrates or other decomposable salts, or even in certain other ways.

It is to be understood that the invention also contemplates the use of mixtures or combinations of these indium compounds, such as, for example, indium phosphomolybdate and indium phosphotungstate.

The manner of working of the catalyst is not known and no explanation of its very pronounced activity can be ofiered at this time. Its specificity for oxidative dehydrogenation of hydrocarbons, particularly olefins to diolefins, is especially advantageous.

The catalyst may be used with or without a filler or carrier material and may be pelleted or formed in other conventional manner. If a carrier is used it is preferably one having a good thermal conductivity and pores of relatively large size such, for instance, as pellets of alundum, crushed fire brick, pumice, or the like. A filler or binding agent in an amount up to about 50% by Weight of the total may be included. Suitable materials are, for example, silica, powdered aluminum, and other inert materials.

Example I An indium phosphate catalyst was prepared as follows. Indium metal was dissolved in 3 molar nitric acid, and to the solution an amount of phosphoric acid stoichiometrically equivalent to the indium was added. Ammonium hydroxide, 3 molar, was then added until the pH was 7.0. The resulting hydrogel was aged overnight, filtered off, and dried. The dry material was calcined 2 hours at 500 C. and broken to 20 mesh white granules. Analysis showed 12.2% P compared to 14.7% by theory for InPO Example If The catalyst described in Example 1 was used to convert l butene to 1,3-butadiene in a small fixed-bed reactor at atmospheric pressure. A mixture of air" and 1- butene with an air/butene ratio of 8.3 was fed to the reactor. The air was actually a mixture of 79.5% argon and 20.5% oxygen, since nitrogen would have interfered with the mass spectrometric analysis of the reaction product stream. The results are shown in the following tabulation. Here the GHSV is the total gaseous hourly space velocity in volumes of gas (0 C., 760 mm.) per volume of catalyst per hour. The selectivity to butadiene is the percentage of the converted l-butene that was The balance of the converted l-butene Went chiefly to CO and CO, with selectivities .to oxygenated compounds such as methyl vinyl ketone in the order of 1% or less.

Conversion, percent Selectiv- Maximum Temperature, GHSV ity to C. C'l t,

,of O2 oil-C4118 ,percent Example III The same catalyst described in Example I1WHS used to convert 2-methyl-2-butene to isoprene. A helium oxygen mixture Was fed in lieu of air. Results were as follows:

Conversion, Selectiv- Maximum percent :ity to Tempera- GHSV He/Gz C5H1o/0r Isoprene, ture, 0. percent of 02 of 051110 "It is to be understood that the tabulated data included herein is illustrative of results obtained at approximately atmospheric pressure.

Example IV An indium phosphate catalyst was prepared by mixing 100 ml. of 0.413 molar In(NO in dilute nitric acid solution with 139 ml. of 3 molar phosphoric'acid, heating to 70 C., and adding 3'1nolar ammonium hydroxide at that temperature until a pH of 8.9' was reached. The precipitate was filtered ofi, washed with dilute ammonia, dried, broken to 1020 mesh white granules, and calcined 2 hours at 500 C. This was more nearly a stoichiometric InPO than the catalyst of Example I.

Example V The catalyst of Example IV was used to convert l-butene to'1,3-butadiene as in Example II,-except that the air/.butene ratio was 5. Results were:

Conversion,

percent Selectivity Maximum Temperature, GHSV to C4HB, 0. percent Of 02 0f 1-C4Hs Thus, activitywas lower than in. Example II, but. selectivity washigher. Almost no. acetone,.acetaldehyde, acrolein, crotonaldehyde, formaldehyde, or furan was formed. Conversion to'methylvinylketone was less than 1%.in all cases.

Example V1 mum temperature of 440 C. the conversion of oxygen was 89%, the conversion of l-butene was 30%, and the selectivity to butadiene was 42%. The balance ofwthe conversion was chiefly to CO and CO, with -6%.se1ectivity to acetaldehyde and 2% to acetone.

.4 Example VII An indium molybdate-silica catalyst was prepared by precipitation from a mixture of 50 ml. of a 0.63 molar indium nitrate in dilute nitric acid solution with 47 ml. of 1 molar ammonium molybdate solution and 16 grams of Ludox silica sol (ammonium form; about 30% SiO by addition of ammonium hydroxide to pH 6. The precipitate was filtered oil, dried, and calcined as 10-20 mesh granules. Some molybdenum was lost in the filtrate and the final creamy yellow catalyst contained In/Mo in a calculated atomic ratio of 1.03. The catalyst was tested as in Example V. At a maximum temperature of 425 C. the conversion of oxygen was 63%, the conversion of 1- butene was 36%, and the selectivity to butadiene was 66%. Conversions to oxygenated compounds other than water and CO were less than 1% Example VIII An indium tungstate-silica catalyst was prepared by mixing 50 ml. of 0.63 molar indium nitrate solution in dilute nitric acid with 472 ml. of 0.1 molar ammonium tungstate solution and 22 g of Ludox silica sol (ammonium form; about 30% w. SiO and adding ammonium hydroxide to pH 6. The precipitate was filtered, dried, and calcined at 500 C. The product was pale yellow. The calculated ratio of In/w. is 2/3. The catalyst was tested as in Example V. At a maximum temperature of 485 C. the conversion of oxygen was 96%, the conversion of l-butene was 48%, and the selectivity to butadiene was 69%. Conversions to oxygenated compounds other than water and CO were less than 0.5%.

I claim as my invention:

1. Process for the selective oxidative dehydrogenation of a C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to produce as the major reaction product a hydrocarbon having the same number of carbon atoms but at least one more ethylenic double bond, which comprises passing the aliphatic hydrocarbon in vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with a solid catalyst therefor consisting essentially of a composition of matter consisting essentially of indium, oxygen and an element selected from the group consisting of phosphorus, molybdenum and tungsten in catalytically efifective proportions at a temperature of from about 300 C. to 600 C. and at a pressure of from about to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

2. Process for the selective oxidative dehydrogenation of C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to produce as the major reaction product a hydrocarbon having the same number of carbon atoms but at least one more ethylenic double bond, which comprises passing the aliphatic hydrocarbon in vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with a solid catalyst therefor consisting essentially of indium phosphate in catalytically effective proportions at a temperature of from about 300 C. to 600 C. and at a pressure of from about 5 to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

3. Process for the selective oxidative dehydrogenation of a C4 '1 monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to produce as the major reaction product a hydrocarbon having the same number of carbon atoms but at least one more ethylenic double bond which comprises passing the first said hydrocarbon in the vapor phase together with about an equal molar amount of oxygen through a reaction zone in contact with a solid catalyst comprising as its main active constituent indium phosphate at a temperature of from about 300 C. to 600 C., a pressure of from about 5 to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

4. Process for the selective oxidative catalytic dehydrogenation of a C 4; monoolefinicaliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with the solid catalyst containing as its main active constituent indium phosphate at a temperature of from about 300 C. to 600 C., a pressure of from about 5 to p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

5. Process for the selective oxidative catalytic dehydrogenation of a C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with a fixed foraminous bed of catalyst containing as its main active constituent indium phosphate at a temperature of from about 300 C. to 600 C., a pressure of from about 5 to 150 p.s.i.a., and recovering the seco-nd-1nentioned hydrocarbon from the reaction product.

6. Process for the selective oxidative catalytic dehydrogenation of a C.; monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with an approximately equal molar quantity of oxygen through a reaction zone in contact with a solid catalyst containing as its main active constituent indium phosphate at a temperature of from about 300 C. to 600 C., a pressure of from about 5 to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

7. Process for the selective oxidative catalytic dehydrogenation of a C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with air in an amount equivalent to from about 0.3 to 2 moles of oxygen through a reaction zone in contact with the solid catalyst containing as its main active constituent indium phosphate at a tem perature of from about 300 C. to 600 C., a pressure of from about 5 to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

8. Process for the selective oxidative catalytic dehydrogenation of C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with a solid catalyst containing as its main active constituent indium phosphate at a temperature of from about 350 C. to 500 C., a pressure of from about 5 to 150 p.s.i.a., and recovering the second-mentioned hydrocarbon from the reaction product.

9. Process for the selective oxidative catalytic dehydrogenation of a C monoolefinic aliphatic hydrocarbon having no quaternary carbon atoms to a corresponding diolefin which comprises passing said hydrocarbon in the vapor phase together with from about 0.3 to 2 moles of oxygen through a reaction zone in contact with a solid catalyst containing as its main active constituent indium phosphate at a temperature of from about 350 C. to 500 C., and at about atmospheric pressure, and recovering the second-mentioned hydrocarbon from the reaction product.

10. Process in accordance with claim 1 wherein the catalyst consists essentially of indium molybdate.

11. Process in accordance with claim 1 wherein the catalyst consists essentially of indium tungstate.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,116 Walker et al July 2, 1935 2,945,900 Alexander et al. July 19, 1960 2,991,321 Voge et al. July 4, 1961 4th... m 

1. PROCESS FOR THE SELECTIVE OXIDATIVE DEHYDROGENATION OF A C4-7 MONOOLEFINIC ALIPHATIC HYDROCARBON HAVING NO QUATERNARY CARBON ATOMS TO PRODUCE AS THE MAJOR REACTION PRODUCT A HYDROCARBON HAVING THE SAME NUMBER OF ARBON ATOMS BUT AT LEAST ONE MORE TEHYLENIC DOUBLE BOND, WHICH COMPRISES PASSING THE ALIPHATIC HYDROCARBON IN VAPOR PHASE TOGETHER WITH FROM ABOUT 0.3 TO 2 MOLES OF OXYGEN THROUGH A REACTION ZONE IN CONTACT WITH A SOLID CATALYST THEREFOR CONSISTING ESSENTIALLY OF A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF INDIUM, OXYGEN AND AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF PHOSPHORUS, MOLYBDENUM AND TUNGSTEN IN CATALYTICALLY EFFECTIVE PROPORTIONS AT A TEMPERATURE OF FROM ABOUT 300*C. TO 600* C. AND AT A PRESSURE OF FROM ABOUT 5 TO 150 P.S.I.A., AND RECOVERING THE SECOND-MENTIONED HYDROCARBON FROM THE REACTION PRODUCT. 